When the monarchy came to an end, the chief sacred functions of the king, and
all that was particularly important on the religious side, passed to the
Pontifex Maximus [PONTIFEX],
but a certain part fell to the Rex Sacrorum, a priest who preserved the name
of king much as the βασιλεὺς did at Athens.
The Romans seem to have wished to preserve a continuity in religious
matters, and not to deprive the gods of the service of the king by their
change of constitution, while they carefully assigned him nothing that could
give him political weight, and precluded him from holding any other office
in the state. It is probable that the ceremonies described below, which fell
specially to him, were regarded as marking particularly the royal
priesthood. The office was not peculiar to Rome; there was a Rex Sacrorum at
Tusculum, Lanuvium, Velitrae, Bovillae, and perhaps at other places (Orell.
2279; C. I. L. 6.2125, 10.8417; Wilmanns, 1773).

The Rex Sacrorum belonged to the collegium of which the Pontifex Maximus was
the head, and the pontifices and flamines were also members [PONTIFEX]. (Cf. Cic. de Dom. 52, 135; de
harusp. Resp. 6, 12; Marquardt, Staatsverw.
iii.2 243.) In the ordosacerdotum he stands first, above the three chief flamines,
and at the priestly banquet he sat in the first place, and next to him the
flamen dialis (Gel. 10.15, cf. Fest. p. 185;
Serv. ad Aen. 2.2; Gel. 15.27). It is probable that this was the
place originally reserved for the king; and perhaps also the appearance of
his wife as assistant in the sacrifices which fell to him, with the title
reginasacrorum (Fest. p. 113; Macrob.
1.15, 19; C. I. L. 6.2123), was a remnant of the king's
priestly office under the monarchy: the wives of flamines, however, also
took part in sacrifices. His traditional royalty appears, too, in the fact
that the pontifices received the februa for the purification from the Rex
and the flamen dialis, and perhaps also, as Mommsen thinks, in his official
residence [see REGIA]. In spite,
however, of these shadows of ancient supremacy, ho ranked below the Pontifex
Maximus in real dignity as well as in political importance (Liv. 2.2) [compare SACERDOS], and this is marked by the mode of his
appointment; and indeed, though, as was said above, standing first in the
ordosacerdotum, the Rex was practically
only a subordinate member of the College of Pontifices, nominated by them,
appointed by the Pontifex Maximus, and inaugurated by the augurs. It appears
that when a vacancy occurred, out of certain persons nominated by the
College of Pontifices, the Pontifex Maximus selected the Rex Sacrerum, who
was then inaugurated by the augurs at the Comitia Calata (Liv. 40.42; Gel.
15.27; Marquardt, Staatsverw. 3.322, note). His office
was for life (Gaius, 1.112; Serv. ad Aen.
8.646), and he was always a patrician (Cic. de Dom. 14, 38; Liv.
6.41).

His duties, so far as our information goes, were as follows: on the calends
of each month, the state of the moon having been announced to him by one of
the pontifices, he summoned the people in Comitia Calata to the Curia
Calabra. on the Capitol, and announced when the nones of that month would
fall, and offered sacrifice there to Janus, while his wife offered in the
Regia (Macrob. 1.15); on the nones the people were again gathered in the Arx
to learn front his declaration (edictum) what
festival days fell in that month, and he offered the sacra nonalia in arce (Varro, L. L. 6.28); on Jan.
9 [AGONIA] he offered a ram to Janus in the Regia
(Fest. p. 10; Varro, L. L. 6.12; Ov. Fast. 1.317). For other ceremonies specially attributed to
the Rex Sacrorum on Feb. 24, March 24, and May 24, see REGIFUGIUM

It was, as has been said, carefully provided, from jealousy of the royal
power, that the Rex Sacrorum should be cut off from political power and
incapable of holding any other office (Liv.
40.42; Plut. Q. R. 63; Dionys. A. R. 4.74). This disability (which did not exist in
other priestly offices) was not always maintained under the Empire, for we
find Cn. Pinarius Severus Rex Sacrorum and Consul under Trajan (C. I.
L. 14.3604, 4246); but still the office being, as will be seen
from the above account, purely ceremonial, and regularly divorced from power
and influence in the state, it became less and less coveted (cf. Liv. 28.6; 40.42),
though it remained till a late period, at any rate till the middle of the
3rd century A.D. (Trebell. Poll. Valer. duo, 6, 6). (See
further in Marquardt, Staatsverw. iii.2
321-324; Mommsen, Staatsrecht, ii.3
13-15. A general survey of the changes in the relative importance of
priestly offices will be found under SACERDOS.)